(1). Field of the Invention
The present invention relates to improvements in drainpipe joints in single-pipe type drainage systems with the omission of a vent pipe in multi-storied buildings.
(2). Description of the Related Art
In a vertical drainpipe installed in a multi-storied building, the flushing action produced at a joint where a horizontal branch pipe joins the vertical pipe, in addition to the suction force induced when sewage discharged from toilet stools, bathtubs and the like and introduced into the vertical pipe falls plumb down, causes negative or positive air pressure to sharply fluctuate. The fluctuation of the air pressure allows the water confined in the trap of the toilet stool or bathtub to be sucked out or the air therein to blow up. As a result, a malodorous gas deriving from the sewage may penetrate into rooms, thus resulting in unsanitary living conditions.
In order to obviate such a discouraging phenomenon, a drainpipe is normally equipped with a vent pipe open to the atmosphere to minimize the fluctuation of the air pressure. The water is thus protectively secured in the trap. FIG. 4 shows a drainage system provided with such a vent pipe, the drainage system comprising horizontal branch pipes 1, a vertical pipe 2, a vent pipe 3, and a vent cap 4 for releasing the sewage gas therefrom to decrease the growth of air pressure.
On the other hand, single-pipe type drainage systems with the omission of such a vent pipe 3 have come into common use partly because the drainage system with the vent pipe 3 requires a large piping space and partly because its piping construction becomes costly.
More specifically, a single drainpipe joint allowing the omission of the vent pipe is often employed in that an S-shaped pipe is provided on the upstream side of a joint where a horizontal branch pipe meets the vertical pipe to reduce not only the suction force produced in the vertical drainpipe but also the falling velocity of sewage which forms the main cause of pressure fluctuation therein, whereas the joint where the horizontal branch pipe joins the vertical pipe is so contrived that the fluctuation of the negative or positive air pressure is minimized.
FIG. 5 shows a drainage system equipped with such single drainpipe joints, the drainage system comprising horizontal branch pipes 1, a vertical pipe 2, a vent cap 4, S-shaped pipes 5, and single drainpipe joints 6.
There are structural variations of the single drainpipe joint 6 having the S-shaped pipe 5 as shown in FIGS. 6 to 8. The single drainpipe joint 6 shown in FIGS. 6a, 6b has an elliptical joint in section having bilevel junction ports 7, 8 of a vertical pipe 9 for a horizontal branch pipe, eccentric branch passages 11 with a partition wall 10 for dividing the upper half of the joint into sections, an S-shaped pipe 5 coupled to the upper ends of the branch passages 11, and an upper-end junction port 5a situated on the vertical axis .lambda. of the vertical pipe 9. The single drainpipe joint 6 shown in FIGS. 7a, 7b has a branch pipe 12 branching off diagonally upwardly from the lower portion of the vertical pipe 9 having the bilevel junction ports 7, 8 for the horizontal branch pipe, the upper half of the branch pipe being vertically eccentric, the S-shaped pipe 5 incorporated with the upper end of the branch pipe 12, and the upper-end junction port 5a situated on the vertical axis .lambda. of the vertical pipe 9.
The single drainpipe joint 6 shown in FIGS. 8a, 8b has the S-shaped pipe 5 directly incorporated with the upper-end of the vertical pipe 9 having the bilevel junction ports 7, 8 for the horizontal branch pipe, and the upper-end junction port 5a situated on the vertical axis .lambda. of the vertical pipe 9.
Each of the aforementioned single drainpipe joints 6 is exceedingly effective in reducing the falling velocity of sewage by means of the S-shaped pipe 5. However, the centrifugal force induced when the sewage changes its course in the bent portion of the S-shaped pipe 5 causes the sewage to swirl and the vortex flow is directed clockwise and counterclockwise from time to time with instability, depending on the falling condition of the sewage. Moreover, the clockwise and counterclockwise whirls occur alternately, which causes the air pressure in the drainpipe to pulsatingly fluctuate and also badly affects the water confined in the trap.